What is the best modern overdrive to put behind a y block and what adapters do I need I have the original I guess 2 speed automatic and its getting tired
The cheapest would be making a custom adapter from a Borg-Warner pattern bell housing to a Tremec 5 speed. There are adapter bell housings at about $2K...Tremec or AOD. Gear Vendors has hang on over drives a $3K but I haven't seen one for a FordOMatic.
Cheapest way out...overhaul the FordOMatic and change the rear ratio. You may have to learn to use manual low (L) and shift to drive (D) for second and third. My Ranch Wagon has a 292 and FordOMatic. I overhauled the FordOMatic ($150) and changed the rear gear from 3.56 to 3.00. It's what Ford did when they rolled out the CruiseOMatic (FordOMatic that automatically shifts 1-2-3). Now I can roll the E-ways at 70 mph+ without cranking 3700 RPMs
I havn't used one but had a link to these. Cost $ 850.00 per the website.
http://www.transmissionadapters.com/ford_y_block.htm
Those old Fordo's require regular maintaince.
Have the bands adjusted, change the filter and fluid and
you may be suprised.
Goodluck,
Ron.
BTW, A divorsed Gear Vendors is the easiest way to go.